Issues with ozone depletion have resulted in an R22 phase out that begins in the year 2010. This has driven the majority of commercial refrigeration installations toward R125 and R143A blend refrigerants having the required zero Ozone Depletion Potential (ODP). On the negative side, these refrigerants have lower system efficiencies than R22 and also have high Global Warming Potential (GWP).
Further developments in refrigeration cooling systems have led to R-32/R-125/R-134A blend refrigerants having a lower Global Warming Potential_(GWP). As a comparison to R-32/R-125/R-134A blend refrigerants, R407A has a GWP of 2110 and R407C has a GWP of 1770, but R125 and R143 blend R404A has a GWP of 3920 and R507 has a GWP of 3985.
A downside of R407A and R407C refrigerants, is that they have large refrigerant glide issues, which can make cooling capacity unstable in the presence of flash gas at the expansion device. The present invention substantially eliminates and/or prevents any occurrence of flash gas at the expansion device due to the refrigerant liquid subcooling. By definition subcooling means that the refrigerant liquid is too cold for the presence of flash gas. Therefore this invention will enhance the performance and reliability of R-32/R-125/R-134A blend refrigerants.
Refrigerant subcooling has been used to raise the system efficiencies. Mechanically coupled subcooling, in particular, has been used for larger refrigeration and air conditioning systems employing the same or similar refrigerants for both the main and the subcooling circuits. The efficiency increase, however, has not been accompanied by any meaningful reduction in GWP.
Certain blended refrigerants are available having zero ODP and low GWP are available for air conditioning application, but have not seen use in commercial refrigeration installations because they have performance issues that make them less practical than alternative refrigerants, i. e. very high discharge pressures, which means large refrigerant pipes with limited pressure ratings cannot be applied to these refrigerants, or significant temperature glide, which means there can be more than one temperature in a refrigerant system at a given pressure. Both present engineering and design problems for service contractors in commercial installations with long pipe runs.
Table 1 below is a summary chart of the characteristics of the refrigerants mentioned above. The data in this table is readily available as common knowledge in commercial refrigeration.
TABLE 1DischargePressure at 120 F.RefrigerantGWPApplicationCondensingR404A3859Refrigeration310psigR5073925Refrigeration322psigR410A1997Air Conditioning418psigR407C1770Refrigeration & Air266-300psigConditioningR221780Refrigeration & Air260psigConditioningR407A2110Refrigeration284psigThe commercial refrigeration systems with subcooling have typically been large, field assembled systems and they have often been problematic from an operational standpoint. The combination of high installed capital cost, high maintenance cost, and limited contractor experience leads refrigerant subcooling technology toward use only on refrigeration systems of 25 Hp, or larger, compressor size. This size limitation works against current public sentiment for higher system efficiency in all size applications without addressing the concurrent sentiment for lower environmental impact.